1. Field of the Invention
The present invention relates to a substrate treatment method and assembly, for example, for removing work objects such as photoresist film or deposits of unwanted organic or inorganic compounds in micromachining processes which include manufacturing processes for semiconductors such as integrated circuits (ICs), large-scale integrations (LSIs), liquid crystal displays (LCDs), printed circuit boards, etc.
2. Description of the Related Art
In micromachining processes for manufacturing processes for semiconductor devices such as ICs, LSIs, etc., photosensitive organic macromolecular compounds are applied to a semiconductor substrate of silicon or the like, or to a glass substrate, a photoresist is developed after exposing the substrate to ultraviolet light through a photomask formed with a predetermined pattern for a circuit, etc., to form a photoresist pattern on the substrate, a film may be formed by chemical vapor deposition (CVD), sputtering, etc., on the portions of the substrate where the photoresist pattern has not been formed, and etching by chemicals, reactive ion etching (RIE), heat diffusion of impurities, and ion implantation may be performed. Then, the film of photoresist remaining on the substrate after this series of treatments is removed by chemical treatment, but in manufacturing processes for LSIs, etc., this operation of applying photoresist and removing the photoresist film after performing a variety of treatments is generally carried out not just once, but several times.
Several methods have been adopted for removing the photoresist film, but since the photoresist film can adversely affect subsequent processes if not completely removed, it is important to ensure that the photoresist film is removed completely. In particular, as the line width of circuitry being formed on semiconductor devices gets finer and finer with the rising the degree of integration that is occurring nowadays, because the effects of photoresist film residue are more of a problem than when integration was lower, complete removal is called for, and this is normally attempted by means of wet processes using a chemical solutions or dry processes using oxygen plasmas or the like.
In photoresist film removal by wet processes, sulfuric acid is normally used and hydrogen peroxide is added to raise the oxidizing capacity of the sulfuric acid. Similarly, in LCD manufacturing processes, special solutions such as 106 solution (30% dimethyl sulfoxide, 70% monoethanolamine) are used. In smear removal from printed circuit boards, chemical solutions such as permanganic acid are used. When these solutions are used to remove the photoresist film and unwanted deposits, it is common to clean with ultrapure water to remove solution remaining after film and deposit removal, and to further remove residue and other deposits.
However, with these methods, it is necessary to use large amounts of chemical solutions which are expensive and have a large environmental impact, and the development of alternative treatment methods is an urgent task. Thus, methods for removing unwanted deposits such as organic matter using ozone gas have been proposed as environmentally friendly substrate treatment methods. Of these, the substrate treatment method disclosed in Japanese Patent Laid-Open No. HEI 5-152270 is an extremely promising method enabling significant improvement in removal speed. This method increases removal speed using wet ozone gas. The construction of the assembly is shown in FIG. 27.
In the drawing, a substrate 2 is placed on a substrate mounting table 3 disposed in a treatment chamber 1, a discharge pipe 13 for discharging gas from the treatment chamber 1 is disposed in the treatment chamber 1, and an ozone decomposition device 40 is connected to the discharge pipe 13. Before treatment with an ozone-containing gas, the inside of the treatment chamber 1 is sealed and gas in the treatment chamber 1 is removed by suction through the discharge pipe 13. The substrate mounting table 3 is mounted on a rotatable shaft and is constructed such that the substrate 2 is rotated as it is being treated with the ozone-containing gas to ensure uniform treatment.
Oxygen is supplied from an oxygen storage tank 43 to an ozone gas generator 6 and the ozone-containing gas generated in the ozone gas generator 6 comes into contact with ultrapure water in a gas-liquid contact device 7, becomes wet, is supplied to the treatment chamber 1 through an ozone-containing gas supply pipe 8, passes through apertures 24 disposed in a gas disperser 5, and acts on work objects on the substrate 2. The gas disperser 5 is composed of quartz, fluorocarbon resin, or the like, and is formed from a perforated plate or a porous sintered body through which gas can pass to enable the ozone-containing gas to be supplied to the surface of the substrate 2 uniformly.
Ozone in the gas discharged from the treatment chamber 1 is broken down by the ozone decomposition device 40 and discharged. An ultrapure water supply nozzle 25 for cleaning the substrate 2 is disposed in the treatment chamber 1 and the surface of the substrate 2 is cleaned with ultrapure water on completion of the treatment. After the treatment is completed, gas remaining inside the treatment chamber 1 is replaced with a gas such as nitrogen, and the substrate 2 is removed from the treatment chamber 1 and dried. Because wet ozone, which is extremely reactive, is supplied to the inside of the treatment chamber 1, inner surfaces of the treatment chamber 1 and surfaces of the devices inside the treatment chamber 1 are composed of quartz, fluorocarbon resin or the like.
Japanese Patent Laid-Open No. HEI 5-152270 states that the speed of photoresist film removal is significantly improved by the use of wet ozone and that removal speeds of approximately 0.2 μm/min were achieved by the substrate treatment method disclosed therein even at room temperature. However, by comparison, the removal speed when using conventional mixed sulfuric acid-hydrogen peroxide-water solutions or the special 106 solution is 1 μm/min or more, making further improvement of removal speed a necessary and indispensable condition to make the above substrate treatment method using wet ozone-containing gas practical, and to date there have been no examples of its actual use.
Generally, the speed of a chemical reaction increases as temperature rises. Consequently, measures which try to achieve practical removal speeds by raising the temperature of the substrate are conceivable. However, as disclosed in paragraph 0017 of Japanese Patent Laid-Open No. HEI 5-152270, it was not possible to speed up the removal speed by the above conventional method in which wet ozone-containing gas was supplied, even when the substrate was heated.